Laser device and exposure device using the same

ABSTRACT

In a laser module, a laser beam which is emitted from a laser element is focused by a condensing optical system and caused to enter an incidence end of an optical fiber. A laser device is provided with a plurality of these laser modules. Emission end portions of the optical fibers are bundled to form a laser emission portion. A thickness of cladding h of each optical fiber is set to a value calculated in accordance with the following equation:  
             cladding             thickness   ⁢           ⁢   h           ≤       (                 emission   ⁢           ⁢   light   ⁢           ⁢   amount               of   ⁢           ⁢   one   ⁢           ⁢   laser   ⁢           ⁢   module   ⁢           ⁢   W                   required             intensity   ⁢           ⁢   C           ×         packing             ratio   ⁢           ⁢   P                 -         core             diameter   ⁢           ⁢   t             )     ÷   2         
As a result, it is possible to emit a laser-beam with a high intensity that is required for functionality as a laser light source, for the purpose of raising resolution of an exposure apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 10/857,547 filed Jun. 1,2004. The entire disclosure of the prior application, application Ser.No. 10/857,547, is considered part of the disclosure of the accompanyingdivisional application and is hereby incorporated by reference.

This application also claims priority under 35 USC 119 from JapanesePatent Application No. 2003-156558, the disclosure of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high-intensity laser device which issuitable for use as a laser light source of an exposure apparatus forexposing an exposure surface at a photosensitive material or the likewith a laser beam which is spatially modulated by a spatial lightmodulation device in accordance with image data.

2. Description of the Related Art

Heretofore, an exposure apparatus which employs a spatial lightmodulation device such as a digital micromirror device (DMD) or the likefor carrying out image exposure with light beams modulated in accordancewith image data has been proposed in Japanese Patent Application No.2002-149888, which is a prior application which has not yet beenpublished.

A DMD thereof is structured as, for example, a mirror device in whichnumerous micromirrors, which alter angles of reflection surfaces thereofin accordance with control signals, are arranged two-dimensionally on asemiconductor support of silicon or the like.

An exposure apparatus which utilizes such a DMD is structured such that,for example, a laser beam emitted from a laser beam-emitting laser lightsource is collimated at a lens system, is reflected at the DMD, which isdisposed substantially at a focusing position of the lens system, passesthrough an aperture, and is focused onto an exposure surface by anotherlens system.

In such an exposure apparatus, control signals are generated inaccordance with image data or the like. Each of the micromirrors of theDMD is controlled to ‘on’ or ‘off’ by an unillustrated control device,on the basis of the control signals, to modulate (deflect) the laserbeam. A portion of (light flux of) the laser beam is blocked by passingthe modulated laser beam through apertures, and spot diameters of thelaser beam are controlled to have a predetermined size at the exposuresurface. In addition, the beam spots are formed with a shape of the beamspots (a spot shape) being a predetermined shape, and the beam spots areirradiated onto the exposure surface for exposing the same.

In this exposure apparatus, a photosensitive material (a photoresist orthe like) is provided at a recording surface. The beam spots which areformed and projected by the apertures are irradiated onto thephotosensitive material from an exposure head of the exposure apparatus.While positions of these beam spots are relatively moved with respect tothe photosensitive material, the DMD is adjusted in accordance with thedata. Thus, a process of pattern-exposure on the photosensitive materialcan be implemented.

For laser light which is emitted from laser devices which are employedat light sources of such exposure apparatuses, higher output is sought.Accordingly, as a laser device which is capable of emitting high-powerlaser light, a multiplex laser light source with a plurality ofsemiconductor laser elements and one multi-mode optical fiber, in whichlaser beams emitted from the plurality of semiconductor laser devicesare multiplexed at the multi-mode optical fiber, has been proposed (see,for example, Japanese Patent Application Laid-Open (JP-A) No.2002-202442).

To provide a laser output that is required in an exposure apparatus, itis necessary to bundle a plurality of these multiplex laser lightsources for use. Further, in order to perform high-precision imaging, itis required that a light source portion has high intensity. However,when these multiplex laser light sources, which conventionally haveemployed commonly-used fibers with a cladding diameter of 125 μm, arebundled, intensity is reduced by an amount corresponding to claddingregions, which do not contribute to light propagation, and the intensityis inadequate for the required intensity.

In order to structure a high-precision exposure system in whichresolution is improved, with a conventional exposure apparatus asdescribed above, a laser device which emits high-intensity laser lightwith a high power that is necessary for functionality as ahigh-precision exposure apparatus is called for.

SUMMARY OF THE INVENTION

In consideration of the circumstances described above, an object of thepresent invention is to provide a new laser device which is capable ofemitting laser light of a high intensity which is required for raisingprecision of performance of an exposure apparatus.

A laser device of a first aspect of the present invention includes:laser elements; optical fibers each including cladding surrounding acore; and a laser emission portion at which emission end portions of aplurality of the optical fibers are arranged in the form of a bundle andintegrated for emitting a single emission beam, the laser emissionportion being provided with a plurality of laser modules that includecondensing optical systems which focus laser beams emitted from thelaser elements and cause the laser beams to enter through incidence endsof the optical fibers, wherein a thickness h of the cladding of each ofthe plurality of optical fibers is set to a value calculated inaccordance with the following equation. $\begin{matrix}{cladding} \\{{thickness}\quad h}\end{matrix} \leq {\left( {\sqrt{\frac{\begin{matrix}{{emission}\quad{light}\quad{amount}} \\{{of}\quad{one}\quad{laser}\quad{module}\quad W}\end{matrix}}{\begin{matrix}{required} \\{{intensity}\quad C}\end{matrix} \times \begin{matrix}{packing} \\{{ratio}\quad P}\end{matrix}}} - \begin{matrix}{core} \\{{diameter}\quad t}\end{matrix}} \right) \div 2}$

When the laser device is structured as described above, etendue ofemitted light which is provided from the laser emission portion, whichis structured in a bundle, is reduced and high-intensity laser light isemitted from a small area. Thus, the laser device has higher intensity.Hence, a laser device can be structured which is capable of emitting alaser beam with a high intensity that is required for functionality as alaser light source for, for example, raising resolution in an exposureapparatus.

A laser device of a second aspect of the present invention includes:laser elements; optical fibers each including cladding surrounding acore; laser modules including condensing optical systems which focuslaser beams emitted from the laser elements and cause the laser beams toenter through incidence ends of the optical fibers; a connectiveemission end portion at which a predetermined number of the opticalfibers, which respectively lead out from the laser modules, are bundledto form a fiber bundle; a multiplex optical fiber, an incidence end ofwhich is connected at the connective emission end portion, the multiplexoptical fiber including a core with a diameter corresponding to an areawhich exceeds an area of the bundle that corresponds to a region of theplurality of bundled cores, such that laser beams that are emittedthrough the connective emission end portion are multiplexed, and themultiplex optical fiber including a numerical aperture equal to orgreater than a numerical aperture of the optical fibers that lead outfrom the laser modules; and a laser emission portion at which emissionend portions of a plurality of the multiplex optical fiber are bundledto form a fiber bundle.

When the laser device is structured as described above, it is possible,by using the multiplex optical fibers which have broad claddingdiameters and high strength for extension, to extend over longdistances, even in a case in which strength of the optical fibers thatlead out from the laser modules has been lowered, because the claddingthickness h thereof has been reduced, and thus the optical fibers areinappropriate for guiding over long distances.

A laser device of a third aspect of the present invention furtherincludes: a focusing lens and a housing, the housing including structuresuch that a multiplexed light beam that is emitted through theconnective emission end portion, at which the plurality of opticalfibers forms the fiber bundle, is focused by the focusing lens andcaused to enter the core of the multiplex optical fiber, and the housingbeing structured in the form of a closed-structure container whichencloses, all together, the connective emission end portion, thefocusing lens and an incidence end portion of the multiplex opticalfiber, a sealed atmosphere which includes an inactive gas being chargedinto the housing.

When the laser device is structured as described above, in addition tothe operation and effects of the second aspect, the connective emissionend portion, at which the plurality of optical fibers are fiber-bundled,can be connected with the incidence end portion of the multiplex opticalfiber with the focusing lens interposed therebetween. In addition, theconnective emission end portion, the incidence end portion of themultiplex optical fiber and the focusing lens, which are enclosed by thehousing, are protected by the sealed atmosphere, which includes aninactive gas or the like and is charged into the housing, such thatadherence of contaminants, such as components of organic materials thatare decomposed by photochemical reactions, dust in the atmosphere andthe like, and deterioration of laser characteristics is avoided.

A laser device of a fourth aspect of the present invention furtherincludes: a first transparent member, which is disposed at an emissionend face of the connective emission end portion, at which the pluralityof optical fibers form the fiber bundle, for preventing adherence ofcontaminants and deterioration of laser characteristics; a secondtransparent member, which is disposed at a face of the incidence end ofthe multiplex optical fiber for preventing adherence of contaminants anddeterioration of laser characteristics; and a focusing lens which isdisposed between the first transparent member and the second transparentmember such that a multiplexed light beam which, after being emittedfrom the emission end face of the connective emission end portion, haspassed through the first transparent member passes through the secondtransparent member and enters the core of the multiplex optical fiber.

When the laser device is structured as described above, in addition tothe operation and effects of the second aspect, the laser beam broadenswhile being transmitted from the emission end face of the connectiveemission end portion to an emission end face of the first transparentmember, the laser beam diameter at the emission end face of the firsttransparent member is wider, and power density is reduced. As a result,adherence of contaminants, such as components of organic materials thatare decomposed by photochemical reactions, dust in the atmosphere andthe like, at the emission end face of the first transparent member anddeterioration of laser characteristics can be avoided. Further, thediameter of the laser beam when focused by the focusing lens andincident at an incidence end face of the second transparent memberwidens and power density is reduced. As a result, adherence ofcontaminants, such as components of organic materials that aredecomposed by photochemical reactions, dust in the atmosphere and thelike, at the incidence end face of the second transparent member anddeterioration of laser characteristics can be avoided.

Further, a fifth aspect of the present invention is an exposure devicecomprising: a laser device which emits a light beam for exposure,wherein the laser device comprises: laser elements; optical fibers eachincluding cladding surrounding a core, and including an incidence endand an emission end portion; and a laser emission portion at whichemission end portions of a plurality of the optical fibers are arrangedin the form of a bundle and integrated for emitting a single emissionbeam, the laser emission portion being provided with a plurality oflaser modules that include condensing optical systems which focus laserbeams emitted from the laser elements and cause the laser beams to enterthrough incidence ends of the optical fibers, wherein a thickness h ofthe cladding of each of the plurality of optical fibers is set to avalue calculated in accordance with the following equation:$\begin{matrix}{cladding} \\{{thickness}\quad h}\end{matrix} \leq {\left( {\sqrt{\frac{\begin{matrix}{{emission}\quad{light}\quad{amount}} \\{{of}\quad{one}\quad{laser}\quad{module}\quad W}\end{matrix}}{\begin{matrix}{required} \\{{intensity}\quad C}\end{matrix} \times \begin{matrix}{packing} \\{{ratio}\quad P}\end{matrix}}} - \begin{matrix}{core} \\{{diameter}\quad t}\end{matrix}} \right) \div 2}$a light modulation device at which a plurality of modulation elements,which respectively change light modulation states thereof, the spatiallight modulation device being for modulating the light beam, which isemitted from the laser device and incident at the plurality ofmodulation elements, at each of the modulation elements; a microlensarray at which a plurality of microlenses are arranged with a pitchcorresponding to the plurality of modulation elements, the microlensarray being for condensing light beams, which have been modulated by themodulation elements, at the respective microlenses; and a focusingoptical system for focusing the light beams which have been condensed bythe microlens array onto a surface to be exposed.

A sixth aspect of the present invention is an exposure devicecomprising: a laser device which emits a light beam for exposure,wherein the laser device comprises: laser elements; optical fibers eachincluding cladding surrounding a core, and including an incidence end;laser modules including condensing optical systems which focus laserbeams emitted from the laser elements and cause the laser beams to enterthrough incidence ends of the optical fibers; a plurality of connectiveemission end portions at each of which a predetermined number of theoptical fibers, which respectively lead out from the laser modules, arebundled to form a fiber bundle; a plurality of multiplex optical fibers,an incidence end of each of which is connected at one of the connectiveemission end portions, the multiplex optical fiber including a core witha diameter corresponding to an area which exceeds an area of the bundlethat corresponds to a region containing the cores of the plurality ofbundled optical fibers, such that laser beams that are emitted throughthe connective emission end portion are multiplexed, and the multiplexoptical fiber including a numerical aperture equal to or greater than anumerical aperture of the optical fibers that lead out from the lasermodules; and a laser emission portion at which emission end portions ofthe plurality of multiplex optical fibers are bundled to form a fiberbundle; a light modulation device at which a plurality of modulationelements, which respectively change light modulation states thereof, thespatial light modulation device being for modulating the light beam,which is emitted from the laser device and incident at the plurality ofmodulation elements, at each of the modulation elements; a microlensarray at which a plurality of microlenses are arranged with a pitchcorresponding to the plurality of modulation elements, the microlensarray being for condensing light beams, which have been modulated by themodulation elements, at the respective microlenses; and a focusingoptical system for focusing the light beams which have been condensed bythe microlens array onto a surface to be exposed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the exterior of an exposureapparatus which is equipped with a laser device relating to anembodiment of the present invention.

FIG. 2 is a perspective view showing structure of a scanner of theexposure apparatus equipped with the laser device relating to theembodiment of the present invention.

FIG. 3A is a plan view showing exposed regions formed on aphotosensitive material at the exposure apparatus equipped with thelaser device of the present invention.

FIG. 3B is a view showing an arrangement of exposure areas due torespective exposure heads at the exposure apparatus equipped with thelaser device of the present invention.

FIG. 4 is a perspective view showing general structure of an exposurehead of the exposure apparatus equipped with the laser device relatingto the embodiment of the present invention.

FIG. 5 is a side view showing general structure of the exposure head ofthe exposure apparatus equipped with the laser device relating to theembodiment of the present invention.

FIG. 6 is a partial enlarged view showing structure of a digitalmicromirror device (DMD) used in the exposure apparatus equipped withthe laser device relating to the embodiment of the present invention.

FIG. 7A is an explanatory view for explaining operation of the DMD usedin the exposure apparatus equipped with the laser device relating to theembodiment of the present invention.

FIG. 7B is an explanatory view for explaining operation of the DMD usedin the exposure apparatus equipped with the laser device relating to theembodiment of the present invention.

FIG. 8A is a plan view showing positions of exposure beams and scanninglines for comparison between a case in which the DMD used in theexposure apparatus equipped with the laser device relating to theembodiment of the present invention is not disposed at an angle and acase of angled disposition.

FIG. 8B is a plan view showing positions of exposure beams and scanninglines for comparison between the case in which the DMD used in theexposure apparatus equipped with the laser device relating to theembodiment of the invention is not disposed at an angle and the case ofangled disposition.

FIG. 9A is a perspective view showing structure of a fiber light sourcewhich is used in the exposure apparatus equipped with the laser devicerelating to the embodiment of the invention.

FIG. 9B is a front view showing an arrangement of light emission pointsat a laser emission portion.

FIG. 10A is a perspective view of principal portions showing structureof a fiber light source which is used at the laser device relating tothe embodiment of the invention.

FIG. 10B is an enlarged sectional view showing an example of structureat a connection portion between a connective emission end portion and amultiplex optical fiber for extension in a fiber light source which isused at the laser device relating to the embodiment of the invention.

FIG. 10C is an enlarged sectional view showing another example ofstructure at a connection portion between a connective emission endportion and a multiplex optical fiber for extension in a fiber lightsource which is used at the laser device relating to the embodiment ofthe invention.

FIG. 11 is a plan view showing structure of a multiplex laser lightsource which is used in the laser device relating to the embodiment ofthe invention.

FIG. 12 is a plan view showing structure of a laser module which is usedin the laser device relating to the embodiment of the invention.

FIG. 13 is a side view showing structure of the laser module shown inFIG. 12.

FIG. 14 is a side view of principal portions showing structure of thelaser module shown in FIG. 12.

DETAILED DESCRIPTION OF THE INVENTION

Below, an embodiment relating to a laser device of the present inventionwill be described in detail with reference to the drawings.

(Structure of Exposure Apparatus)

The laser device relating to the present embodiment is structured to beusable in an exposure apparatus which exposes an exposure surface, at aphotosensitive material or the like, with a light beam which isspatially modulated by a spatial light modulation device in accordancewith image data.

As shown in FIG. 1, an exposure apparatus 151 is provided with a flatboard-form stage 152, which attracts, by suction, and retains asheet-form photosensitive material 150 at a surface thereof. Two guides158, which extend in a stage movement direction, are provided at anupper face of a thick board-form equipment pedestal 156, which issupported at four leg portions 154. The stage 152 is disposed such thata longitudinal direction thereof is oriented in the stage movementdirection, and is supported by the guides 158 so as to be reciprocallymovable. At this exposure apparatus 151, an unillustrated drivingapparatus is provided for driving the stage 152 along the guides 158.

At a central portion of the equipment pedestal 156, an ‘n’-like gate 160is provided so as to straddle a movement path of the stage 152.Respective end portions of the gate 160 are fixed at two side faces ofthe equipment pedestal 156. Sandwiching the gate 160, a scanner 162 isprovided at one side and a plurality (for example, two) of detectionsensors 164 are provided at the other side. The detection sensors 164detect a leading end and a trailing end of the photosensitive material150. The scanner 162 and the detection sensors 164 are respectivelymounted at the gate 160, and are fixedly disposed upward of the movementpath of the stage 152. The scanner 162 and detection sensors 164 areconnected to an unillustrated controller which controls the scanner 162and detection sensors 164.

As shown in FIGS. 2 and 3B, the scanner 162 is equipped with a plurality(for example, fourteen) of exposure heads 166, which are arrangedsubstantially in a matrix pattern with m rows and n columns (forexample, three rows and five columns). In this example, in considerationof width of the photosensitive material 150, four of the exposure heads166 are provided in the third row. Note that when an individual exposurehead which is arranged in the m-th row and the n-th column is to bereferred to, that exposure head is denoted as exposure head 166 _(mn).

Exposure areas 168 covered by the exposure heads 166 have, for example,rectangular shapes with short sides thereof in a scanning direction. Insuch a case, in accordance with movement of the stage 152, band-formexposed regions 170 are formed on the photosensitive material 150 at therespective exposure heads 166. Note that when an exposure area that isformed by an individual exposure head, which is arranged in the m-th rowand the n-th column, is to be referred to, that exposure area is denotedas exposure area 168 _(mn).

As shown in FIGS. 3A and 3B, in each row, the respective exposure heads,which are arranged in a line, are disposed to be offset by apredetermined interval in a row arrangement direction (which interval isan integer multiple (two in the present embodiment) of the longdimension of the exposure areas), such that the band-form exposedregions 170 will be lined up without gaps therebetween in a directionintersecting the scanning direction. Consequently, a portion that cannotbe exposed between exposure area 168 ₁₁ and exposure area 168 ₁₂ of thefirst row can be exposed by exposure area 168 ₂₁ of the second row andexposure area 168 ₃₁ of the third row.

As shown in FIGS. 4 and 5, at each of the exposure heads 166 ₁₁ to 166_(mn), a digital micromirror device (DMD) 50 is provided to serve as aspatial light modulation device for modulating incident light beams atrespective pixels in accordance with image data. The DMD 50 is connectedwith a controller 51, which is provided with a data processing sectionand a mirror driving control section.

This controller 51 is structured by a computer which, although notillustrated, is provided with a CPU, data storage devices such as a ROMand a RAM, input/output devices such as a monitor, a keyboard and thelike, and the like.

A light source 66, at a light incidence side of the DMD 50, illuminatesthe DMD 50. A lens system 67 is also provided. The lens system 67corrects laser light which is emitted from the light source 66, andfocuses the light on the DMD 50.

Lens systems 72 and 74, which magnify a DMD image that has beenreflected at the DMD 50, are provided at a light reflection side of theDMD 50.

A microlens array 76 is disposed at a position at which the DMD image isfocused by the lens systems 72 and 74. At the microlens array 76,microlenses are provided in correspondence with the respective pixels ofthe DMD. An aperture array 78 is disposed at a light emission side ofthe microlens array 76. Lens systems 54 and 58 are disposed at a lightemission side of this aperture array 78 such that the DMD 50 and anexposure surface 56 have a conjugative relationship.

At this exposure apparatus 151, when image data is inputted to thecontroller 51, driving signals are generated for driving control of eachmicromirror of the DMD 50 on the basis of the inputted image data.Angles of reflection surfaces of the respective micromirrors of the DMD50 are controlled in accordance with the generated control signals.

Light that is irradiated from the light source 66 through the lenssystem 67 to the DMD 50 is reflected in predetermined directions inaccordance with the angles of the reflection surfaces of the respectivemicromirrors, and is thus modulated. The modulated light is magnified bythe lens systems 72 and 74. As a result, a size on the exposure surface56 of spots corresponding to pixels of the DMD 50 is magnified, and apitch of these pixel spots is magnified.

The light that has been magnified by the lens systems 72 and 74 entersthe respective microlenses that are provided at the microlens array 76,and the magnified DMD images are shrunk again. Here, because all lightflux enters the microlens array 76, light usage efficiency is notreduced.

The light that has been focused by the microlens array 76 passes throughthe respective apertures provided at the aperture array 78 and entersthe lens systems 54 and 58 and an image of the DMD 50 is focused at theexposure surface 56 by the lens systems 54 and 58. Note that theoccurrence of ghost images due to stray light is prevented by the lightpassing through these apertures.

As shown in FIG. 6, at the DMD 50, very small mirrors (micromirrors) 62,which are supported by support pillars, are disposed on an SRAM cell(memory cell) 60. The DMD 50 is a mirror device which is structured witha large number (for example, 600 by 800) of these extremely smallmirrors, which structure image elements (pixels), arranged in acheckerboard pattern. At each pixel, as shown in FIGS. 7A and 7B, themicromirror 62 is provided so as to be supported at an uppermost portionof the support pillar. A material with high reflectivity, such asaluminium or the like, is applied by vapor deposition at the surface ofthe micromirror 62.

The reflectivity of the micromirror 62 is at least 90%. The SRAM cell60, which is fabricated with CMOS silicon gates by a continuoussemiconductor memory production line, is disposed directly under themicromirror 62, with the support pillar, which includes a hinge and ayoke, interposed therebetween. The whole of this structure is monolithic(integrated).

When digital signals are written to the SRAM cell 60 of the DMD 50, themicromirrors 62 supported at the support pillars are inclined, about adiagonal, in a range of ±α° (for example, ±10°), relative to the side ofthe support at which the DMD 50 is disposed. FIG. 7A shows a state inwhich the micromirror 62 is inclined at +α°, which is an ‘ON’ state, andFIG. 7B shows a state in which the micromirror 62 is inclined at −α°,which is an ‘OFF’ state. Accordingly, as a result of control of theinclinations of the micromirrors 62 at the pixels of the DMD 50 inaccordance with image signals, as shown in FIG. 6, the light that isincident at the DMD 50 is reflected in directions of inclination of therespective micromirrors 62.

FIG. 6 shows a portion of the DMD 50 enlarged, and shows an example of astate in which the micromirrors 62 are controlled to +α° and −α°. TheON-OFF control of the respective micromirrors 62 is carried out by thecontroller 51 connected to the DMD 50. Light that is reflected by themicromirrors 62 in the ON state is modulated to an exposing state andenters a projecting optical system which is provided at the lightemission side of the DMD 50, as is shown in FIG. 5. Light that isreflected by the micromirrors 62 in the OFF state is modulated to anon-exposing state and enters a light-absorbing body (not shown).

It is preferable if the DMD 50 is disposed to be slightly inclined, suchthat a short side thereof forms a predetermined angle θ (for example, 1°to 5°) with the scanning direction. FIG. 8A shows scanning tracks ofreflection images (exposure beams) 53 formed by the micromirrors in acase in which the DMD 50 is not inclined. FIG. 8B shows scanning tracksof the exposure beams 53 in a case in which the DMD 50 is inclined.

At the DMD 50, a large number (for example, 800) of micromirrors arearranged in a long side direction (a row direction) to form amicromirror row, and a large number (for example, 600) of thesemicromirror rows are arranged in a short side direction. As shown inFIG. 8B, when the DMD 50 is inclined, a pitch P2 of scanning paths(scanning lines) of the exposure beams 53 from the micromirrors istighter than a pitch P1 of scanning lines in the case in which the DMD50 is not inclined. Thus, resolution can be greatly improved. However,because the angle of inclination of the DMD 50 is very small, a scanningwidth W2 in the case in which the DMD 50 is inclined is substantiallythe same as a scanning width W1 in the case in which the DMD 50 is notinclined.

Hence, substantially the same positions of the same scanning lines(dots) will be superposingly exposed by different micromirror rows(multiple exposure). As a consequence of this multiple exposure,exposure positions can be controlled in very fine amounts, andhigh-precision exposure can be implemented. Further, by control in veryfine amounts of exposure positions at boundary lines between theplurality of exposure heads arranged in the direction intersecting thescanning direction, joins without steps can be formed.

Instead of inclining the DMD 50, the micromirrors may be disposed in astaggered pattern in which the micromirror rows are shifted bypredetermined intervals in the direction intersecting the scanningdirection, and the same effects can be obtained.

(Structure of High-Intensity Laser Device)

As shown in, for example, FIG. 9A, the fiber light source 66 is equippedwith a plurality (for example, twenty-five) of “pigtail”-type lasermodules 64. From each laser module 64, an optical fiber 30 is led out.In a case in which a plurality of single-mode laser diodes, a multi-modelaser diode or the like is employed, a multi-mode optical fiber is usedfor the optical fiber 30. In a case in which a single single-mode laserdiode is employed, a single-mode optical fiber may be used as theoptical fiber 30.

As shown in FIGS. 9A and 9B, at end portions of this plurality ofoptical fibers 30 leading out from the respective laser modules 64,emission end portions of the optical fibers 30 (light emission points)are arranged in a single row, without gaps, along the directionintersecting the scanning direction and bundled to structure a laseremission portion 68. Note that the light emission points could bebundled so as to be arranged in two rows along the directionintersecting the scanning direction.

This arrangement in which the emission end portions of the opticalfibers 30 are bundled is, as described later, determined in accordancewith a spot shape of beam spots that are projected at the exposuresurface 56.

When this plurality of emission end portions of the optical fibers 30 isbundled, integration of the plurality of emission end portions of theoptical fibers 30 into a rectangular form may be implemented by fusionwith glass or fixing with solder. Further, the plurality of emission endportions of the optical fibers 30 may be integrated by being sandwichedbetween two rectangular flat plates.

Furthermore, a transparent protective plate 63, of glass or the like, isdisposed at the light emission side of the bundled plurality of opticalfibers 30 in order to protect end faces of the optical fibers 30. Theprotective plate 63 may be disposed to be closely contacted with the endfaces of the optical fibers 30, and further, may be disposed such thatthe end faces of the optical fibers 30 are sealed in an inactive gassuch as nitrogen gas or the like, or an inactive gas including a smallamount of oxygen gas.

The emission end portions of the optical fibers 30 emit laser light withhigh optical density, tend to attract dust, and are susceptible todeterioration. When these emission end portions are protected by theprovision of the protective plate 63, accumulation of dust at the endfaces can be prevented and deterioration can be slowed.

At the optical fibers 30, any of step index-type optical fibers, gradedindex-type optical fibers and multiplex-type optical fibers can be used.For example, a step index-type optical fiber produced by MitsubishiCable Industries, Ltd. may be used. In the present embodiment, theoptical fibers 30 are step index-type optical fibers.

The optical fibers 30 that are employed may have, for example, claddingdiameter=60 μm, core diameter=50 μm and NA=0.2.

Commonly, with laser light in the infrared region, propagation lossesincrease as the cladding diameter of an optical fiber becomes smaller.Accordingly, suitable cladding diameters are determined in accordancewith a wavelength range of laser light. However, the shorter thewavelength, the smaller the propagation losses. Hence, with laser lightwith a wavelength of 405 nm, as emitted from a GaN-based semiconductorlaser, propagation losses are barely increased at all when a claddingthickness ((cladding diameter−core diameter)/2) is set to around half acladding thickness for a case of propagating infrared light in an 800 nmwavelength region or around a quarter of a cladding thickness for a caseof propagating infrared light in a 1.5 μm wavelength region, the latterof which is used for communications. Therefore, the cladding diametercan be reduced to 60 μm.

The cladding diameter of the optical fibers 30 is not limited to 60 μm.An optical fiber which is employed in a conventional fiber light sourcehas a cladding diameter of 125 μm. However, because focusing depthbecomes deeper as the cladding diameter becomes smaller, it ispreferable if the cladding diameter of these multi-mode optical fibersis 80 μm or less, more preferably 60 μm or less, and even morepreferably 40 μm or less. On the other hand, given that the corediameter needs to be at least 3 to 4 μm, it is preferable that thecladding diameter of the optical fiber 30 is at least 10 μm.

Thus, at the light source 66, which serves as a high-intensity laserdevice, laser light is emitted from the laser emission portion 68 whichis structured by bundling the end portions of the optical fibers 30 thatlead out from each of the plurality of laser modules 64. Next, atechnique for setting intensity of this laser light to a high intensity,which is needed for performance that is required of the exposure heads166 of the exposure apparatus 151, will be described.

Reducing etendue (numerical aperture×area of a light emission region) iseffective for increasing resolution at the exposure apparatus 151.Accordingly, in order to implement a high resolution that is requiredfor functionality of the exposure apparatus 151, it is necessary toenable the emission of higher intensity laser light by reducing, by arequired area amount, the area of a light emission region of the laseremission portion 68, which region is structured by bundling the endportions of the plurality of optical fibers 30 that lead out from eachof the plurality of laser modules 64.

Further, as a technique for reducing the area of the light emissionregion of the bundled laser emission portion 68 by the required area,there is a technique in which an area that cladding 30B encompasses isreduced by a portion corresponding to the required area. The cladding30B is provided around a core 30A of the optical fiber 30.

Accordingly, thickness of the cladding 30B at the optical fibers 30 isderived and specified in accordance with an intensity of laser light forrealizing the resolution that is required for functionality of theexposure apparatus 151.

An intensity C of the laser light that is emitted from the bundled laseremission portion 68 can be found from the following equation:Intensity C≦(light amount W emitted from a single laser module×number ofmodules n)÷(optical fiber area A×number of optical fibers N×packingratio P)

Here, the optical fiber area A=π×(core diameter t×cladding thickness h).

The packing ratio P=optical fiber area A×number of optical fibersN÷light emission region area SB.

Further, in this laser device, number of modules n=number of opticalfibers N Deriving a formula for the required cladding thickness h fromthe above produces the following equation 1: $\begin{matrix}{cladding} \\{{thickness}\quad h}\end{matrix} \leq {\left( {\sqrt{\frac{\begin{matrix}{{emission}\quad{light}\quad{amount}} \\{{of}\quad{one}\quad{laser}\quad{module}\quad W}\end{matrix}}{\begin{matrix}{required} \\{{intensity}\quad C}\end{matrix} \times \begin{matrix}{packing} \\{{ratio}\quad P}\end{matrix}}} - \begin{matrix}{core} \\{{diameter}\quad t}\end{matrix}} \right) \div 2}$

That is, as a technique for setting a high intensity, the present laserdevice is structured by: plurally providing the pigtail-type lasermodules 64 (fiber modules), which serve as laser light sources in whichlaser light from laser diodes that is incident from one ends, which areincidence ends, of the optical fibers 30 is emitted from the other ends,which are emission ends, of the optical fibers 30; providing the laseremission portion 68, which is structured with a fiber bundle by bundlingand integrating the emission end portions of the plurality of opticalfibers 30 which lead out from each of the plurality of laser modules 64,for emitting a single emission beam; and setting the thickness h ofcladding of each of the optical fibers 30 to a value calculated inaccordance with the above equation.

As a result, the etendue of emission light which is provided from thelaser emission portion 68 which is structured with a fiber bundle isreduced, and intensity of the laser light source is raised such thathigh-intensity laser light is emitted from a small area.

Thus, a laser device which is capable of emitting the high-intensitylaser beam that is required for performance as a laser light source forraising resolution of the exposure apparatus 151 can be structured.

Further, the optical fibers 30 which lead out from the pigtail-typelaser modules 64 need to be fibers which propagate the laser beamswithout loss. Therefore, a minimum value of the cladding thickness h atthese optical fibers 30 is subject to structuring with a thickness whichis greater than a region of effusion of evanescent light into thecladding.

In the case of a structure in which the thickness h of the cladding ofeach optical fiber 30 is set to a value calculated in accordance withequation 1, it is possible to make the thickness h of the cladding ofthe optical fibers 30 greater than a minimum value thereof, such that astrength of each optical fiber 30 is not lowered more than necessary.

Next, a specific structure will be described for a case in which theexposure apparatus 151 is structured as, for example, a high-precisionexposure system with a line spacing of 20 μm, and in which it isrequired that a beam diameter on the exposure surface is set to not morethan 7 μm.

In each laser module 64 in such a case, single-mode laser beams B1 to B7enter a multi-mode optical fiber with core diameter 50 μm with acoupling efficiency of 0.76. Respective outputs of GaN-basedsemiconductor lasers at each laser module 64 are 30 mW. Thus, 160 mW (30mW×7×0.76) multiplexed beams are provided at emission ends of theoptical fibers of the modules.

In order to realize high-precision exposure with a line spacing of 20 μmat the exposure apparatus 151, it is required that beam diameters at thephotosensitive material are not more than 7 μm. Furthermore, with regardto light output, depending on sensitivity of the photosensitivematerial, exposure speed and light usage efficiency of an exposureoptical system, an output of 4 W is required at the fiber bundle end.

A size of each pixel of the DMD in this exposure apparatus 151 is 13 μmby 13 μm, and the number of pixels that are employed is 128 by 1024.Thus, an illumination area of light from the bundle is 22.2 mm² (1.66mm×13.31 mm).

The beams with pixel pitch 13 μm from the pixels of the DMD are coupledby a focusing optical system at a face of a microlens array with afocusing distance of 20 μm and a lens pitch of 39 μm, and are focused bythe microlenses. An image of this focusing plane is projected onto thephotosensitive material surface by an imaging optical system forexposure.

For the focused beam spots to be less than 7 μm, it is necessary that anillumination numerical aperture of the DMD is not more than 0.02. Inorder to illuminate, via the lens system 67, with an NA of 0.02 or lessat this area of the DMD, it is necessary that an illumination area ofthe laser light at which the NA 0.2 fibers are bundled is not more than0.22 mm².

In order to provide an output of 4 W, it is necessary to bundletwenty-five of the multi-mode optical fibers (4 W/160 mW=25).

Now, in a case in which a multi-mode optical fiber, of a type which isused in conventional fiber modules, with core diameter 50 μm, claddingdiameter 125 μm and NA 0.2 is employed, the area of the light emissionregion is 0.39 mm² (i.e., an area when multi-mode optical fibers withcladding diameters of 125 μm are formed into a square of five columnsand five rows, which is 125 μm×5×125 μm×5=0.39 mm²). Thus, the intensityis 10.24 W/mm² (4 W/0.39 mm²=10.24 W/mm²), which is insufficient withrespect to the intensity that is required for the device.

In contrast, when the aforementioned equation 1 is applied, a requiredcladding thickness of not more than 22 μm (a cladding diameter of 94 μmor less) is found. Considering tolerances of the respective opticalelements, a cladding diameter of 80 μm or less is desirable, and morespecifically, a cladding diameter of 60 μm or less is more desirable.

Further, if a fiber with core diameter 50 μm and cladding diameter 60 μmis used, the area of the illumination region will be 0.09 mm² (60μm×5×60 μm×5=0.09 mm²). Thus, the intensity will be at least four timesthat in the case in which the conventional fibers with cladding diameter125 μm are used.

Further, if, for example, the optical fibers 30 in this high-precisionexposure system with line spacing 20 μm are set to a core diameter of 30μm and a cladding diameter of 40 μm, the etendue of the emitted lightprovided by the laser emission portion 68 that is structured at thefiber bundle will be further reduced, and the laser device can be raisedin intensity, with the high-intensity laser light being emitted from aneven smaller area.

Next, a technique for appropriately structuring the optical fibers whichlead out from the light source 66, which serves as a high-intensitylaser device, to be extended over a long distance for use, even in acase in which the cladding thickness of the optical fibers 30 that leadout from the laser modules 64 has been reduced as described above, willbe described with reference to FIGS. 10A, 10B and 10C.

As shown in FIG. 10A, in a structure which enables extension of theoptical fibers of the high-intensity laser device over a long distance,a predetermined number, for example, seven, of the optical fibers 30which are structured with a thin cladding thickness h and lead out fromseven of the laser modules 64 are bundled, are integrated into acylindrical form by means of fusion with glass, fixing with solder orthe like, and form a connective emission end portion 200 which isstructured at the emission end portions of the optical fibers 30.

An incidence end face of a multiplex optical fiber for extension 202 isfixed at an emission end face of this connective emission end portion200 for connection.

At a portion of connection of the connective emission end portion 200with the multiplex optical fiber for extension 202, the emission endface of the connective emission end portion 200 is disposed in a statein which a plurality (in this example, seven) of the cores 30A of theoptical fibers 30 are bundled. Thus, the multiplexed light beams areemitted through the connective emission end portion 200.

Accordingly, the multiplex optical fiber for extension 202 is structuredby an optical fiber with a core diameter of at least the diameter of acircle that could be inscribed to contain the bundled plurality (in thisexample, seven) of the cores 30A without any portion of the cores 30Aextending thereoutside. Furthermore, the multiplex optical fiber forextension 202 is structured by a fiber having an NA (numerical aperture)equal to or greater than the NA of the optical fibers 30 that aredisposed at the connective emission end portion 200.

In other words, this connective emission end portion 200 is connected tothe incidence end of the multiplex optical fiber for extension 202 whichhas a core diameter exceeding the area of the bundle that is multiplexedat the connective emission end portion 200 and which has an NA equal toor greater than that of the optical fibers 30 which are employed in thebundle.

This multiplex optical fiber for extension 202 is formed with a lengththat is required to extend the optical fibers from the light source 66over a long distance for use. Furthermore, these multiplex opticalfibers for extension 202 are provided in a predetermined number for onelight source 66, which number is the total number of the laser modules64 that structure that light source 66 divided by the number of theoptical fibers 30 that are bundled at each connective emission endportion 200.

As shown in FIG. 10A, at emission end portions of the predeterminednumber of multiplex optical fibers for extension 202, the emission endportions (light emission points) of the multiplex optical fibers forextension 202 are arranged in a single row without gaps along thedirection intersecting the scanning direction and bundled to structurethe laser emission portion 68.

With this technique for appropriately structuring the optical fibersthat lead out from the light source 66 to extend over a long distancefor use, even in a case in which, because the cladding thickness h hasbeen reduced, the strength of the optical fibers 30 that lead out fromthe laser modules 64 is low and is insufficient for extension over longdistances, extension over long distances is enabled to the extent of themultiplex optical fiber for extension 202, which has large claddingthickness and high strength.

Next, for the technique for appropriately structuring the optical fibersthat lead out from the light source 66 to extend over long distances foruse, an example of another structure of the connection portion betweenthe connective emission end portion 200 and the incidence end face ofthe multiplex optical fiber for extension 202 will be described withreference to FIG. 10B.

A connection portion shown in FIG. 10B is structured such that themultiplexed light beams which are emitted from the connective emissionend portion 200 are focused by a focusing lens 204 and caused to enter acore 202A of the multiplex optical fiber for extension 202.

In addition, a protective structure is provided at the connectionportion shown in FIG. 10B in order to prevent contaminants from adheringto the connective emission end portion 200, the focusing lens 204 andthe incidence end portion of the multiplex optical fiber for extension202 and causing deterioration of laser characteristics.

This protective structure is a structure for preventing contaminants,such as components of organic materials that are decomposed byphotochemical reactions, dust in the atmosphere and the like, fromadhering at the emission end face of the connective emission end portion200, the incidence end of the multiplex optical fiber for extension 202and surfaces of the focusing lens 204 (which is an optical component),in accordance with increases in power and intensity of the laser deviceemitting high-energy ultraviolet laser light (i.e. as power densityincreases), and thus adversely affecting laser characteristics.

Accordingly, at the connection portion shown in FIG. 10B, a housing 206is provided which constitutes a container-like closed structure whichencloses the emission end of the connective emission end portion 200,the focusing lens 204 and the incidence end portion of the multiplexoptical fiber for extension 202 all together.

The connective emission end portion 200, the focusing lens 204 and theincidence end portion of the multiplex optical fiber for extension 202that are disposed inside this housing 206 are subjected to metallizingtreatments. Gas inside the housing 206 is replaced with an inactive gas,after which the housing 206 is metallically sealed with an unillustratedlid.

The inactive gas which is charged into this housing 206 is desirablynitrogen (purity 99.99%) which contains oxygen with a density of 1 ppmor more and at least one of halogen gases and halide gases.

When the sealed atmosphere includes oxygen with a density of 1 ppm ormore, degradation of the laser module can be suppressed. The provisionof this degradation-suppression effect is because the oxygen containedin the sealed atmosphere oxidizes and decomposes solids that aregenerated by photo-decomposition of hydrocarbon compounds. If the oxygendensity is less than 1 ppm, the degradation-suppression effect will notbe obtained. However, as the oxygen density becomes higher,photochemical reactions with organic silicon compound gases arepromoted. Therefore, the oxygen density in the sealed atmosphere ispreferably in a range of 1 to 800 ppm and particularly preferably in arange of 1 to 100 ppm.

The halogen gases are chlorine gas (Cl₂), fluorine gas F₂) and so forth,and the halide gases are gaseous compounds which include halogen atomssuch as chlorine atoms (Cl), bromine atoms (Br), iodine atoms (I),fluorine atoms (F) and so forth.

Examples of halide compounds include CF₃C1, CF₂Cl₂, CFCl₃, CF₃Br, CCl₄,CCl₄—O₂, C₂F₄Cl₂, C₁—H₂, PC1 ₃, CF₄, SF₆, NF₃, XeF₂, C₃F₈, CHF₃ and thelike. However, compounds of fluorine or chlorine with carbon (C),nitrogen (N), sulphur (S), and xenon (Xe) are preferable, and compoundsincluding fluorine atoms are particularly preferable.

A degradation-suppression effect is exhibited even by a tiny amount ofhalogen gas. However, in order to obtain a significantdegradation-suppression effect, it is preferable to set an inclusiondensity of halogen gas to 1 ppm or more. This degradation-suppressioneffect is provided by the halogen gas included in the sealed atmospheredecomposing deposits that are caused by photo-decomposition of organicsilicon compound gases.

If a material having reactivity with respect to the halogen gas, such asa compound of silicon (Si), molybdenum (Mo), chromium (Cr), Tin (Sn) orzirconium (Zr), a nitride or the like, is employed as a surfacemostmaterial covering the optical components, the surfacemost layers ofthese optical components will be etched, and reliability of the modulewill be reduced.

Therefore, at surfacemost layers of the connective emission end portion200, the focusing lens 204 and the incidence end portion of themultiplex optical fiber for extension 202 that are exposed to the sealedatmosphere, it is preferable to use a material which is inactive withrespect to the halogen gas, such as, for example, an oxide or nitride ofindium (In), gallium (Ga), aluminium (Al), titanium (Ti) and tantalum(Ta).

Further, although not illustrated, an air circulation apparatus may beinstalled at the housing 206. This air circulation apparatus has astructure which is provided, at piping which draws the inactive gas outthrough an exhaust aperture provided at the housing 206 and continues toa supply aperture provided at the housing 206, with a filter, a pump anda valve. The filter removes contaminants, the pump circulates theinactive gas, and the valve regulates supply of the gas from a gasstorage cylinder.

For this filter, it is preferable to use a filter which is charged withan adsorbent. As the adsorbent, a zeolite adsorbent, active carbon, orboth a zeolite adsorbent and active carbon can be used. ZEOLUM F9 HA,produced by Tosoh Corporation, is a preferable zeolite adsorbent. ThisZEOLUM F9 HA is formed with a crystalline hydrous aluminosilicate of analkali metal or alkaline earth metal (Me/x.Al₂O₃.mSiO₂.nH₂O: where Me isa metallic ion with valency x). It is desirable to determine the amountof the zeolite adsorbent with consideration to volume of the system, thecontaminants that will be deposited and adsorbence capacity of theadsorbent. The filter is not limited to zeolite type adsorbents;adsorbents which are formed with other compositions can be used.

Further still, a catalyst such as Pt, Pd or the like may be added in thefilter which is charged with the adsorbent, and the filter may be heatedto, for example, 500° C. so as to decompose hydrocarbon compounds.

It is also possible to adhere an adsorbent, with inorganic or organicadhesive, at locations in the housing 206 that are not on optical pathsof the laser beams, as a means for eliminating contaminants.

Next, for the technique for appropriately structuring the optical fibersthat lead out from the light source 66 to extend over long distances foruse, an example of yet another structure of the connection portionbetween the connective emission end portion 200 and the incidence endface of the multiplex optical fiber for extension 202 will be describedwith reference to FIG. 10 c.

The connection portion shown in FIG. 10C is structured by fusinglyproviding a first transparent member 208 at the end face of theconnective emission end portion 200 and fusingly providing a secondtransparent member 210 at the incidence end face of the multiplexoptical fiber for extension 202. Thus, the multiplexed light beams whichare emitted from the connective emission end portion 200 pass throughthe first transparent member 208, are then focused by the focusing lens204, and are caused to enter the core 202A of the multiplex opticalfiber for extension 202 after passing through the second transparentmember 210.

The first transparent member 208 and the second transparent member 210constitute protective structures which prevent contaminants fromadhering at the emission end face of the connective emission end portion200 and the incidence end face of the multiplex optical fiber forextension 202, respectively, and causing deterioration of lasercharacteristics.

The first transparent member 208 and second transparent member 210 whichserve as protective structures are each formed of transparent glass orformed of transparent plastic. At opposite sides of the firsttransparent member 208 and second transparent member 210 from facesthereof that are to be fixed to, respectively, the emission end face ofthe connective emission end portion 200 and the incidence end face ofthe multiplex optical fiber for extension 202, faces of the other endsof the first transparent member 208 and second transparent member 210serve as emission windows. The first transparent member 208 and secondtransparent member 210 are formed as transparent bodies which are shapedto have sizes sufficient to allow widening of the laser beams beyondouter diameters of the connective emission end portion 200 and themultiplex optical fiber for extension 202 (and in the presentembodiment, are formed in cylindrical shapes).

The emission end face of the connective emission end portion 200, theincidence end face of the multiplex optical fiber for extension 202, anincidence face of the first transparent member 208 and an emission faceof the second transparent member 210 are each subjected to end-facecoating so as to be non-reflective with respect to oscillationwavelengths of the multiplexed laser beams, and are structured so as toprevent reflection by air layers and thus raise beam transmissivity.

In a case of a structure in which a required thickness of the firsttransparent member 208 is, for example, around 2 mm, an angle of thelaser beams from the emission end face of the connective emission endportion 200 to the emission end face of the first transparent member 208is 16.5°. Therefore, a laser beam diameter at the emission end face ofthe first transparent member 208 is broadened, and power density isreduced to around a thousandth in comparison to the laser beams at theemission end face of the connective emission end portion 200. As aconsequence, the adherence of contaminants such as components of organicmaterials that are decomposed by photochemical reactions, dust in theatmosphere and the like at the emission end face of the firsttransparent member 208 and the deterioration of laser characteristicscan be avoided.

Moreover, because the diameter of a laser beam that has been focused bythe focusing lens 204 and is about to enter the incidence end face ofthe second transparent member 210 is broad and power density thereof islowered, the adherence of contaminants such as components of organicmaterials that are decomposed by photochemical reactions, dust in theatmosphere and the like at the incidence end face of the secondtransparent member 210 and the deterioration of laser characteristicscan be avoided.

Next, a specific structural example of the laser module 64, which isstructured to serve as a multiplexed laser light source (a fiber lightsource), will be described with reference to FIG. 11.

This multiplex laser light source is structured with a plurality (forexample, seven) of chip-form lateral multi-mode or single-mode GaN-basedsemiconductor lasers LD1, LD2, LD3, LD4, LD5, LD6 and LD7, collimatorlenses 11, 12, 13, 14, 15, 16 and 17, a single condensing lens 20, andone of the multi-mode optical fibers 30. The GaN-based semiconductorlasers LD1 to LD7 are fixedly arranged on a heat block 10. Thecollimator lenses 11 to 17 are provided in correspondence with theGaN-based semiconductor lasers LD1 to LD7, respectively.

Note that the number of semiconductor lasers is not limited to seven.For example, with a multi-mode optical fiber with cladding diameter=60μm, core diameter=50 μm and NA=0.2, it is possible for the light of asmany as twenty semiconductor lasers to be incident therein, and it ispossible to realize an illumination head with a required light amountwhile further reducing the number of optical fibers.

As the GaN-based semiconductor lasers LD1 to LD7, lasers may be utilizedwhich are provided with an oscillation wavelength different from theaforementioned 405 nm, in a wavelength range of 350 nm to 450 nm.

The laser module 64 may be structured with one or a plurality ofmulti-mode lasers replacing the GaN-based semiconductor lasers LD1 toLD7. Such a case may be structured such that, for example, fourmulti-mode lasers structured with excitation layer widths of 8 μm arearranged so as to irradiate at the 50-μm core. Further, the laser module64 may be structured by replacing all seven of the GaN-basedsemiconductor lasers LD1 to LD7 with a single multi-mode laser, forexample, a multi-mode laser with an excitation layer width of 15 μm, andreplacing the optical fiber 30 with an optical fiber with a narrowercore diameter, for example, with a core diameter of 20 μm and a claddingdiameter of 30 μm.

As shown in FIGS. 12 and 13, the above-described multiplex laser lightsource, together with other optical elements, is accommodated in abox-like package 40 which opens upward. The package 40 is provided witha package lid 41 prepared so as to close the opening of the package 40.After an air removal treatment, a sealed gas is introduced and theopening of the package 40 is closed by the package lid 41. Thus, theabove-described multiplex laser light source is hermetically sealed in aclosed space formed by the package 40 and the package lid 41.

A baseplate 42 is fixed at a lower face of the package 40. The heatblock 10, a condensing lens holder 45 and a fiber holder 46 are attachedat an upper face of the baseplate 42. The condensing lens holder 45retains the condensing lens 20. The fiber holder 46 retains an incidenceend portion of the multi-mode optical fiber 30. An opening is formed ina wall face of the package 40. An emission end portion of the multi-modeoptical fiber 30 is led out through this opening to outside the package.

A collimator lens holder 44 is attached at a side face of the heat block10, and retains the collimator lenses 11 to 17. Openings are formed in alateral wall face of the package 40. Wiring 47, which supplies drivingcurrent to the GaN-based semiconductor lasers LD1 to LD7, is passedthrough these openings and led out to outside the package.

Note that in FIG. 12, in order to alleviate complexity of the drawing,of the plurality of GaN-based semiconductor lasers, only the GaN-basedsemiconductor laser LD7 is marked with a reference numeral, and of theplurality of collimator lenses, only the collimator lens 17 is markedwith a reference numeral.

FIG. 14 shows the collimator lenses 11 to 17 and mounting portionsthereof, as viewed from front faces thereof. Each of the collimatorlenses 11 to 17 has a long, narrow, cut-down shape with parallel flatfaces defining a region that includes an optical axis of a circular-formlens which is provided with an aspherical surface. The collimator lenseswith this long, narrow shape may be formed by, for example,molding-formation of resin or optical glass. The collimator lenses 11 to17 are closely disposed in a direction of arrangement of light emissionpoints of the GaN-based semiconductor lasers LD1 to LD7 (the left-rightdirection in FIG. 14) such that the length directions of the collimatorlenses 11 to 17 cross the direction of arrangement of the light emissionpoints.

As the GaN-based semiconductor lasers LD1 to LD7, lasers are employedwhich are provided with an active layer with a light emission width of 2μm, and which respectively emit laser beams B1 to B7 in forms whichwiden at angles of, for example, 10° and 30° with respect, respectively,to a direction parallel to the active layers and a directionperpendicular to the active layers. These GaN-based semiconductor lasersLD1 to LD7 are disposed such that the light emission points thereof arelined up in a single row in the direction parallel to the active layers.

Accordingly, the laser beams B1 to B7 emitted from the respective lightemission points are irradiated to, respectively, the collimator lenses11 to 17 having the long, narrow forms described above, in states inwhich the direction for which the spreading angle of the beam is greatercoincides with the length direction of the lens and the direction inwhich the spreading angle is smaller coincides with a width direction ofthe lens (a direction intersecting the length direction).

The condensing lens 20 is cut away in a long, narrow shape with parallelflat faces defining a region that includes an optical axis of acircular-form lens which is provided with an aspherical surface, and isformed in a shape which is long in the direction of arrangement of thecollimator lenses 11 to 17 (i.e., the horizontal direction) and short ina direction perpendicular thereto. The condensing lens 20 is also formedby, for example, molding-formation of resin or optical glass.

(Operation of Exposure Apparatus)

Next, operation of the exposure apparatus 151 described above will bedescribed.

At each exposure head 166 of the scanner 162, the respective laser beamsB1, B2, B3, B4, B5, B6 and B7, which are emitted in divergent forms fromthe respective GaN-based semiconductor lasers LD1 to LD7 that structurethe multiplex laser light sources of the fiber light source 66, areconverted to parallel light by the corresponding collimator lenses 11 to17, as shown in FIG. 11. The laser beams B1 to B7 that have beencollimated are focused by the condensing lenses 20, and converge at theincidence end faces of the cores 30A of the multi-mode optical fibers30.

In the present embodiment, a condensing optical systems is structured bythe collimator lenses 11 to 17 and the condensing lens 20, and amultiplexing optical system is structured by the condensing opticalsystem and the multi-mode optical fiber 30. Thus, the laser beams B1 toB7 focused by the condensing lenses 20 as described above enter thecores 30A of the multi-mode optical fibers 30, are propagated in theoptical fibers, multiplexed to single laser beams B, and emitted fromthe multi-mode optical fibers 30.

At this exposure apparatus 151, image data corresponding to an exposurepattern is inputted at the controller 51 connected to the DMD 50, and istemporarily stored in a frame memory in the controller. This image datais data which represents a density of each pixel structuring an imagewith a binary value (whether or not a dot is to be recorded).

The stage 152, to which the surface of the photosensitive material 150is attracted by suction, is moved along the guides 158 at a constantspeed by the unillustrated driving apparatus, from an upstream side ofthe gate 160 to a downstream side thereof. When the stage 152 is passingunder the gate 160, and the leading end of the photosensitive material150 has been detected by the detection sensors 164 mounted at the gate160, the image data stored in the frame memory is read out in sequenceas a plurality of line portion units, and control signals for each ofthe exposure heads 166 are generated on the basis of the image data readfrom the data processing section. Hence, the micromirrors of the DMDs 50at the respective exposure heads 166 are respectively switched on andoff by the mirror driving control section in accordance with the controlsignals that have been generated.

When laser light is irradiated from the fiber array light source 66 tothe DMD 50, if a micromirror of the DMD 50 is in the ON state, thereflected laser light is focused on the exposure surface 56 of thephotosensitive material 150 by the lens systems 54 and 58. Thus, thelaser light emitted from the fiber light source 66 is turned on or offat each pixel, and the photosensitive material 150 is exposed in a unit(the exposure area 168) with a number of pixels substantially the sameas the number of pixels employed at the DMD 50. As the photosensitivematerial 150 is moved together with the stage 152 at the constant speed,the photosensitive material 150 is scanned in a direction opposite tothe stage movement direction by the scanner 162, and the strip-formexposed regions 170 are formed at the respective exposure heads 166.

When scanning of the photosensitive material 150 by the scanner 162 hasbeen completed and the trailing end of the photosensitive material 150has been detected by the detection sensors 164, the stage 152 is drivenback along the guides 158 by the unillustrated driving apparatus, to astart point at an upstream-most side of the gate 160, and is again movedalong the guides 158, at the constant speed, from the upstream side tothe downstream side of the gate 160.

As described above, the exposure apparatus of the present embodiment isprovided with exposure heads which illuminate spatial light modulationdevices with fiber light sources at which emission end portions ofoptical fibers (light emission points) of multiplex laser light sourcesare arranged in arrays. At these fiber light sources, cladding diametersof emission ends of the optical fibers are set to be smaller to theextent of a required diameter. Consequently, light emission portiondiameters can be made smaller, and a rise in intensity of the fiberlight sources is enabled. As a result, deeper focusing depths can beprovided, and high-speed, high-precision exposure is enabled. Therefore,the exposure apparatus of the present embodiment can be used forprocesses of exposing thin-film transistors (TFT) and the like, forwhich high intensity is required.

As is described above, with the laser device of the present invention,there are effects in that a high intensity which is required for raisingprecision of performance of an exposure apparatus is provided, and astructure capable of emitting high-intensity laser light is possible.

1. A laser device comprising: laser elements; optical fibers eachincluding cladding surrounding a core, and including an incidence end;laser modules including condensing optical systems which focus laserbeams emitted from the laser elements and cause the laser beams to enterthrough incidence ends of the optical fibers; a plurality of connectiveemission end portions at each of which a predetermined number of theoptical fibers, which respectively lead out from the laser modules, arebundled to form a fiber bundle; a plurality of multiplex optical fibers,an incidence end of each of which is connected at one of the connectiveemission end portions, the multiplex optical fiber including a core witha diameter corresponding to an area which exceeds an area of the bundlethat corresponds to a region containing the cores of the plurality ofbundled optical fibers, such that laser beams that are emitted throughthe connective emission end portion are multiplexed, and the multiplexoptical fiber including a numerical aperture equal to or greater than anumerical aperture of the optical fibers that lead out from the lasermodules; and a laser emission portion at which emission end portions ofthe plurality of multiplex optical fibers are bundled to form a fiberbundle.
 2. The laser device of claim 1, further comprising a focusinglens and a housing at each connective emission end portion, the housingincluding a structure such that a light beam that is emitted through theconnective emission end portion, at which the plurality of opticalfibers forms the first fiber bundle, is focused by the focusing lens andcaused to enter the core of the multiplex optical fiber, and the housingbeing structured in the form of a closed-structure container whichencloses, all together, the connective emission end portion, thefocusing lens and an incidence end portion of the multiplex opticalfiber, a sealed atmosphere which includes an inactive gas being chargedinto the housing.
 3. The laser device of claim 1, further comprising, ateach connective emission end portion: a first transparent member, whichis disposed at an emission end face of the connective emission endportion, at which the plurality of optical fibers form the first fiberbundle, for preventing adherence of contaminants and deterioration oflaser characteristics; a second transparent member, which is disposed ata face of the incidence end of the multiplex optical fiber forpreventing adherence of contaminants and deterioration of lasercharacteristics; and a focusing lens which is disposed between the firsttransparent member and the second transparent member such that a lightbeam which, after being emitted from the emission end face of theconnective emission end portion, has passed through the firsttransparent member passes through the second transparent member andenters the core of the multiplex optical fiber.
 4. The laser device ofclaim 1, wherein an arrangement of the bundled emission end portions isdetermined on the basis of shapes of beam spots that are to be projectedat an object of exposure.
 5. The laser device of claim 1, wherein theoptical fibers that lead out from the laser modules each comprise oneselected from the group consisting of step index-type optical fibers,graded index-type optical fibers and multiplex-type optical fibers. 6.The laser device of claim 1, wherein a cladding diameter of the opticalfibers that lead out from the laser modules is between 10 μm and 80 μm.7. The laser device of claim 1, wherein a cladding diameter of theoptical fibers that lead out from the laser modules is between 10 μm and60 μm.
 8. The laser device of claim 1, wherein a cladding diameter ofthe optical fibers that lead out from the laser modules is between 10 μmand 40 μm.
 9. A laser device comprising: a plurality of laser modules,each including at least one laser element, an optical fiber includingcladding surrounding a core, and including an incidence end, and acondensing optical system which focuses a laser beam emitted from the atleast one laser element and causes the laser beam to enter through theincidence end of the optical fiber; a plurality of connective emissionend portions, at each of which the optical fibers that lead out from apredetermined number of the laser modules are bundled to form a firstfiber bundle; a plurality of multiplex optical fibers each including anincidence end and an emission end portion, the incidence end beingconnected at one of the connective emission end portions, the multiplexoptical fiber including a core with a diameter corresponding to an areawhich encompasses an area that corresponds to the cores of the bundledoptical fibers and the multiplex optical fiber including a numericalaperture equal to or greater than a numerical aperture of the bundledoptical fibers, such that laser beams that are emitted through theconnective emission end portion are multiplexed; and a laser emissionportion at which the emission end portions of the plurality of multiplexoptical fibers are bundled to form a second fiber bundle.
 10. Anexposure device comprising: a laser device which emits a light beam forexposure, wherein the laser device comprises: laser elements; opticalfibers each including cladding surrounding a core, and including anincidence end and an emission end portion; and a laser emission portionat which emission end portions of a plurality of the optical fibers arearranged in the form of a bundle and integrated for emitting a singleemission beam, the laser emission portion being provided with aplurality of laser modules that include condensing optical systems whichfocus laser beams emitted from the laser elements and cause the laserbeams to enter through incidence ends of the optical fibers, wherein athickness h of the cladding of each of the plurality of optical fibersis set to a value calculated in accordance with the following equation:$\begin{matrix}{cladding} \\{{thickness}\quad h}\end{matrix} \leq {\left( {\sqrt{\frac{\begin{matrix}{{emission}\quad{light}\quad{amount}} \\{{of}\quad{one}\quad{laser}\quad{module}\quad W}\end{matrix}}{\begin{matrix}{required} \\{{intensity}\quad C}\end{matrix} \times \begin{matrix}{packing} \\{{ratio}\quad P}\end{matrix}}} - \begin{matrix}{core} \\{{diameter}\quad t}\end{matrix}} \right) \div 2}$ a light modulation device at which aplurality of modulation elements, which respectively change lightmodulation states thereof, the spatial light modulation device being formodulating the light beam, which is emitted from the laser device andincident at the plurality of modulation elements, at each of themodulation elements; a microlens array at which a plurality ofmicrolenses are arranged with a pitch corresponding to the plurality ofmodulation elements, the microlens array being for condensing lightbeams, which have been modulated by the modulation elements, at therespective microlenses; and a focusing optical system for focusing thelight beams which have been condensed by the microlens array onto asurface to be exposed.
 11. An exposure device comprising: a laser devicewhich emits a light beam for exposure, wherein the laser devicecomprises: laser elements; optical fibers each including claddingsurrounding a core, and including an incidence end; laser modulesincluding condensing optical systems which focus laser beams emittedfrom the laser elements and cause the laser beams to enter throughincidence ends of the optical fibers; a plurality of connective emissionend portions at each of which a predetermined number of the opticalfibers, which respectively lead out from the laser modules, are bundledto form a fiber bundle; a plurality of multiplex optical fibers, anincidence end of each of which is connected at one of the connectiveemission end portions, the multiplex optical fiber including a core witha diameter corresponding to an area which exceeds an area of the bundlethat corresponds to a region containing the cores of the plurality ofbundled optical fibers, such that laser beams that are emitted throughthe connective emission end portion are multiplexed, and the multiplexoptical fiber including a numerical aperture equal to or greater than anumerical aperture of the optical fibers that lead out from the lasermodules; and a laser emission portion at which emission end portions ofthe plurality of multiplex optical fibers are bundled to form a fiberbundle; a light modulation device at which a plurality of modulationelements, which respectively change light modulation states thereof, thespatial light modulation device being for modulating the light beam,which is emitted from the laser device and incident at the plurality ofmodulation elements, at each of the modulation elements; a microlensarray at which a plurality of microlenses are arranged with a pitchcorresponding to the plurality of modulation elements, the microlensarray being for condensing light beams, which have been modulated by themodulation elements, at the respective microlenses; and a focusingoptical system for focusing the light beams which have been condensed bythe microlens array onto a surface to be exposed.
 12. The exposuredevice of claim 11, wherein the laser device further comprising afocusing lens and a housing at each connective emission end portion, thehousing including a structure such that a light beam that is emittedthrough the connective emission end portion, at which the plurality ofoptical fibers forms the first fiber bundle, is focused by the focusinglens and caused to enter the core of the multiplex optical fiber, andthe housing being structured in the form of a closed-structure containerwhich encloses, all together, the connective emission end portion, thefocusing lens and an incidence end portion of the multiplex opticalfiber, a sealed atmosphere which includes an inactive gas being chargedinto the housing.